It is known to deposit a magnetically oriented film on substrates by the steps of (1) selecting a suitable substrate, (2) placing the substrate in a chamber, (3) removing the air from the chamber to create a vacuum, (4) subjecting the substrate to a magnetic field that is contrtolled both with respect to its direction of orientation and intensity, and (5) depositing nickel iron or permalloy or any other suitable material onto the substrate by means of a suitable procedure such as, for example, by sputtering. The sputtering operation is continued until the deposition layer is of the required thickness. The above procedure is used to produce thin film material having magneto-resistive properties. Magneto-resistive materials are used in the thin film rad heads of magnetic writing and reading devices.
Typically, the substrate on which the magnetic film is to be deposited is positioned in a vacuum chamber with the entire chamber, including the substrate, being subjected to a magnetic field produced by large coils exterior to the chamber. Such an arrangement is shown by J. K. Howard in the Journal of Vacuum Science Technology A, 4, 1, on pages 1 through 13 of the January/February 1986 issue. Such an arrangement is also discussed by T. R. McGuire and R. I. Potter in the IEEE Transactions on Magnetics, Mag.11, 1018, July 1975 on pages 1018 through 1038. It is also known to provide the required oriented magnetic field by simply placing a magnet on the back of the substrate. This method uses the fringing fields from the magnet for orientation. However, depending on the magnet size, the field is not very uniform over significant area. Thus, with this procedure, only a substrate having a small area can be used. This is discussed by Yasuhiro Nagai and Tomoyuki Toshima in the Journal of Vacuum Science Technology, A, 4, 2364, 1986 on pages 2364 through 2368.
While the above procedures are reasonably suitable for use when only a single substrate at a time is to be produced, they are inadequate for the mass production of substrates having oriented magnetic fields since only a single substratea can be produced at a time if precision control of the produced filed is to be achieved. While a plurality of substrates could perhaps be positioned adjacent one another in a vacuum chamber and be subjected to a single magnetic field and a sputtering operation, the results produced by such a procedure would not be acceptable since the magnetic orientation of the plurality of substrates would not be identical. It is desirable that the substrates and the thin film heads in which the substrates are used, have a magnetic orientation that differ from each other by no more than by an amount termed an error angle. This angle must be within plus or minus 4 degrees from a specified direction of magnetic orientation. Thus, while a plurality of substrates could be produced at the same time from a single magnetic field merely by placing the plurality of substrates within the magnetic field of a single magnet, the resultant devices produced by this procedure would not be commercially acceptable since they would have differing directions of magnetic orientation. It can therefore be seen that it is a problem to produce in high volumes a plurality of substrates each of which has a magnetic orientation equal to the other concurrently produced substrate.